Cross-Tenant Message Recall in Exchange Online

Since we launched the cloud-based Message Recall feature in April 2023 (check out our article on Cloud-based Message Recall in Exchange Online), we’ve been busy enhancing its functionality. This includes support for Outlook on various platforms, notifications for recipients when a message is recalled, limits on how long after sending a message you can recall it, and compatibility with external round-trip messaging (learn more in our Exchange Online Message Recall Updates).

Until now, all these features had one limitation: Message Recall was restricted to a single tenant. Today, we’re excited to introduce a highly anticipated enhancement:

• Cross-Tenant Message Recall, managed through a tenant admin’s allow list.

For privacy reasons, Message Recall was designed to stay within the boundaries of the Exchange Online service and had only been available for messages exchanged within the same Microsoft 365 tenant. As a result, when someone attempted to recall a message sent to recipients outside their tenant, the request would fail, even if those organizations collaborated closely and trusted each other.

Our customers pointed out this issue. Partners, subsidiaries, and affiliated businesses wanted the same recall experience across tenant boundaries as they enjoyed within their own tenants.

With Cross-Tenant Message Recall, a tenant administrator can add other Microsoft 365 tenants to an allow list. Once included, senders from those allowed tenants can successfully recall messages they sent to recipients in the receiving tenant, just like they would for recalls within their own tenant.

The power lies with the receiving tenant—the organisation whose users received the original messages. A cross-tenant recall will only be recognised if the admin of the receiving tenant has added the sender’s tenant to the allow list. This setup ensures that the receiving organisation has full control over which external tenants can recall messages from its users. By default, this feature is turned off; cross-tenant recalls won’t occur until an admin adds at least one tenant to the allow list.

Let’s take a look at two companies, Contoso and Fabrikam, which both use Microsoft 365:

1. A Contoso admin adds Fabrikam’s tenant to Contoso’s cross-tenant recall allow list.
2. A sender at Fabrikam decides to recall a message they previously sent to a recipient at Contoso.
3. Because Contoso has allowed Fabrikam, the recall goes through, just like a standard recall for a message sent within Contoso.

If Fabrikam isn’t on Contoso’s allow list, the recall won’t work, and the sender at Fabrikam will receive a status report indicating that the message cannot be recalled across different organisations. The allow list controls this feature, allowing each organisation to choose independently which external tenants can recall messages from their mailboxes.

Admins can configure all these settings using Exchange Online PowerShell. Here’s how:

To enable or disable cross-tenant message recall for your tenant, use the following command. Setting this to $True activates the feature, while $False (default) turns it off:

Set-CrossTenantRecallConfiguration -CrossTenantRecallEnabled [$true | $false]

If you want to specify external tenants to include or remove from the allowed list, add the IDs of organisations you trust to perform recalls like this:

Set-CrossTenantRecallConfiguration -AllowedSenderTenantIds @{Add="",""}; {Remove="",""}

When a sender from an allowed tenant recalls a message, recipients in the receiving tenant will have the same experience as if it were an intra-tenant recall. If the receiving tenant has notifications enabled for recalls, those will apply to cross-tenant recalls as well. However, if the sender’s tenant isn’t on the receiving tenant’s allow list, the sender will be informed that the message can’t be recalled across organisations.

The deployment of Cross-Tenant Message Recall will commence globally, including in GCC, GCC High, DoD, and Microsoft 365 operated by 21Vianet, starting in mid-August and finishing up by mid-September. We hope this new feature proves beneficial for you, and we’re eager to hear your feedback.

The Microsoft 365 Messaging Team